The 2G/3G radio network based access system includes a core network (CN), a radio access network (such as a Universal Terrestrial Radio Access Network (UTRAN)), and user equipment (UE), where the radio access network includes a radio network controller (RNC) and a radio base station (or referred to as Node B), and a distributed base station is an important form of the radio base station. As shown in FIG. 1, a distributed base station includes a base band unit (BBU) and a remote radio unit (RRU). The interface of the radio distributed base station is a bus interface between the BBU and the RRU, where the bus interface is generally an optical interface or may be an electrical interface. The BBU is a small-sized box-type device; the RRU is an outdoor remote radio device, which is mounted directly on the metal mast or on the wall near the antenna. The interface between the BBU and the RRU is connected via one or several specific signal links, and includes any of the three types: a Common Public Radio Interface (CPRI), IR interface, and Open Base Station Architecture Initiative (OBSAI) interface, with the mainstream rate more than 1228.8 M. The interface of the distributed base station in Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) mode is IR interface, for which each link is at high-speed serial digital transmission rate. Currently, the commercial mainstream rate is 2457.6 Mb/s, which may, in future, be 3.0720 Gb/s or higher. Transmission on the links for interface signals of radio distributed base station between the BBU and the RRU is realized by consuming optical fiber resources. How many channels of interface signals of the distributed base station can be borne by optical fiber influences both the requirements on optical fiber resources in the existing network during networking of the distributed base station and the costs of transmitting the interface signals of the distributed base station. Transmission technology can impact the efficiency of operating and maintaining networks.
In the prior art, the Wavelength Division Multiplexing (WDM) technology is applied for signal transmission between the BBU and the RRU. That is, as shown in FIG. 2, a WDM wavelength is adopted for each channel of interface signals of the distributed base station in the radio base band pool of the BBU. The four channels of signals in FIG. 2 respectively adopt λ1, λ2, λ3, and λ4, which are transmitted after being processed by an optical wavelength splitting/merging module. At remote radio unit of the receiving end, received optical signals are firstly processed by the optical wavelength splitting/merging module, and then the separated optical signals are transmitted to corresponding remote radio module. Due to attenuation of the optical signals transmitted in the optical fiber, for the optical signals that need to pass long transmission distance, an optical amplifier can be added in the optical path to amplifying the optical signals during transmission. In this way, longer transmission distance can be realized, and system monitoring can be performed by setting a system monitoring module in the system.
During the implementation of the present invention, the inventor finds that: In the prior art, each channel of the interface signals of the distributed base station needs to occupy an optical wavelength, which leads to low transmission efficiency during transmission between the BBU and the RRU.